Orthotic devices and appliances, commonly referred to as “orthotics,” have been utilized for many years by orthotists, physical therapists, and occupational therapists. Orthotics assist in the rehabilitation of a patient's joints and associated skeletal systems. Generally orthotics act to support and protect the joint, while alleviating pain associated with joint movement.
There are multiple types of osteoarthritis with different effects on the human knee joint.
Primary osteoarthritis is usually related to aging. With aging the water content of the cartilage increases and the protein makeup of the cartilage degenerates. Repetitive use of the joints over the years can irritate and inflame the cartilage, causing joint pain and swelling. Eventually, cartilage begins to degenerate by flaking or forming tiny crevasses. In advanced cases, there is a total loss of cartilage cushion between the femur and tibia bones at the knee joint. This loss leads to diminished joint space on the affected side of the knee, in turn causing pain and joint mobility limitations. Inflammation of the cartilage can also stimulate new bone outgrowths, or spurs, to form around the joints, in turn causing increased pain and joint inflammation.
Important components of patient care include minimizing the progression of the damage to the cartilage of the knee joint and preventing the formation of bone spurs from bone-on-bone contact during knee joint bending. In a normal knee the soft cartilage layers between the femur (upper leg bone of the knee) and the tibia (lower leg bone of the knee) are separated by a thin layer of synovial fluid. The synovial fluid provides lubrication and prevents direct contact between the cartilage layers.
In a patient with osteoarthritis or osteoarthrosis the cartilage has degraded. The result is no longer smooth cartilage surfaces sliding across one-another while lubricated by synovial fluid, but instead rough cartilage surfaces rubbing against one another directly. This rubbing is the source of osteoarthritis/osteoarthrosis pain.
Bone spurs may form as a result of this joint irritation. These bone spurs sometimes cause bits of bone and cartilage to detach. These detached pieces of bone float within the knee joint, causing further damage.
Damage to the knee is often isolated to a certain portion of the knee joint. In fact, the most common form of osteoarthritis or osteoarthrosis is unicompartmental, meaning that only one of the three compartments of the knee joint is significantly affected by the loss of cartilage padding.
The human knee has three compartments. The medial compartment of is on the inside of the centerline of the body, closest to the knee of the other leg. The lateral compartment of the knee is furthest from the centerline of the body. Finally, the patellar compartment is in the center-upper portion of the knee, to the rear of the patella or knee cap.
The majority of osteoarthritis cases are medial compartment degeneration. Thus, the cartilage or cushioning of the knee joint has significantly deteriorated on the inside portion of the knee. As a result of cartilage degeneration within the medial compartment of the knee the knee becomes imbalanced. The imbalance results in a knee that bows outward. This is often called a “bowleg” condition, referred to as a varus deformity of the knee joint, or genu varum.
A knee joint with bowleg deformity places significant force on the medial compartment of the knee, resulting in joint pain.
Alternatively, a patient will have damage to the lateral compartment of the knee. The result is again an unbalanced knee, with the knee bending inwards at the knee joint. The result is a knock-kneed appearance, or valgus deformity of the knee joint.